1. Field of the Invention
This invention relates to aberrated imaging systems having a variable opto-mechanical component (for example, a variable aperture), in which a filter bank is used to compensate the aberrations introduced at different opto-mechanical settings.
2. Description of the Related Art
Electro-optic imaging systems typically include imaging optics (e.g., a lens or mirror assembly), an electronic sensor array (e.g., CCD detector array) and a digital image processor (e.g., typically implemented in dedicated chips or software). Traditional methods for designing these systems generally involve fairly independent steps. The optics typically is designed with the goal of forming a high quality intermediate optical image at the sensor array. The digital image processing typically is designed after the optics, with the goal of compensating for remaining defects in the sampled intermediate optical image.
The design stages typically occur with little coordination between the optical designer and the image processing designer. One drawback to the traditional design approach is that synergies between the optics and the digital image processing subsystem may be overlooked. The optical designer creates the “best” optical subsystem without knowledge of the digital image processing subsystem. The image processing designer creates the “best” digital image processing subsystem without the ability to modify the previously designed optical subsystem. These subsystems are then “glued” together.
There has been recent interest in taking advantage of these possible synergies. For example, U.S. patent application Ser. No. 11/155,870 “End-To-End Design of Electro-Optic Imaging Systems” to Robinson and Stork concerns a general approach to designing an imaging system by allowing the imaging optics and image processing to compensate each other. Thus, while neither the optics nor the image processing may be optimal when considered alone, the interaction of the two produces good results. Put in another way, in order to achieve a certain overall image quality, this approach allows the use of lower quality optics and/or lower quality image processing so long as the two compensate each other to achieve the desired performance.
However, the situation becomes more complicated when the imaging optics has a variable opto-mechanical component that can be set to different settings. Adjusting the opto-mechanical settings changes the aberrations introduced by the imaging optics. Variable aperture optical systems are one example of a variable opto-mechanical component. For well-corrected imaging optics, changing the aperture size (f-number) may not be much of an issue since a system that is well-corrected at an open aperture setting will still be well-corrected at a more closed aperture setting. However, in the synergistic approach, the imaging optics typically is not well-corrected. For example, the imaging optics might suffer from significant spherical aberration. Adjusting the aperture setting changes the amount of spherical aberration. This, in turn, will require different image processing to compensate for the different amount of aberration. Thus, the system at F/4 may require certain filters and the system opened up to F/2 may require different filters. Storing different filter coefficients for different F/#'s requires increasing the memory requirements and circuit complexity for the image processing subsystem. Other examples of variable opto-mechanical systems include zoom systems and image stabilization systems using mechanical lens tilt or decentration.
Thus, there is a need for approaches that allow different filters to be applied to compensate for different aberrations, but in a more efficient manner.